Coccidiosis is a widespread poultry disease which is produced by infections of protozoa of the genus Eimeria which causes severe pathology in the intestines and ceca of poultry. Some of the most significant of these species are E. tenella, E. acervulina, E. necatrix, E. brunetti and E. maxima. This disease is generally spread by the birds picking up the infectious organism in droppings on contaminated litter or ground, or by way of food or drinking water. The disease is manifested by hemorrhage, accumulation of blood in the ceca, passage of blood in the droppings, weakness and digestive disturbances. The disease often terminates in the death of the animal, but the fowl which survive severe infections have had their market value substantially reduced as a result of the infection. Coccidiosis is, therefore, a disease of great economic importance and extensive work has been done to find new and improved methods for controlling and treating coccidial infections in poultry.
Trypanosomiasis is a term used to describe a group of allied protozoal diseases, each of which is due to infection with a species of the genus Trypanosoma. They reach their greatest importance in Africa where their presence in enzootic form precludes the keeping of domestic animals throughout the largest part of the continent between 15.degree. N and 20.degree. S latitude. The pathogenic trypanosomes of Africa are considered to be primarily associated with the tsetse flies (glossina) which feed on vertebrate blood. Wherever tsetse are present, trypanosomiasis will also be found in some part of the mammalian population. The clinical findings are typically those of a wasting disease with intermittent fever. Anemia, edema, and cachexia are parts of the syndrome.
The important trypanosomes pathogenic to domestic animals are T. congolense, T. simiae, T. vivax, and T. brucei. The latter trypanosome is morphologically identical to T. gambiense, responsible for human "sleeping sickness" of Africa. A trypanosome found in the Western Hemisphere is T. cruzi, which affects both domestic animals and man.
Malaria is a serious parasitic infection normally transmitted by the bite of an infected anopheles mosquito, although it may also be produced by transfusion of blood from an infected donor. It is found most frequently in the tropics and in some tropical areas is hyperendemic. In man it is caused most frequently by the parasites Plasmodium falciparum, P. vivax and P. malariae. The acute phase of the disease is characterized by shaking chills, high fever, sweats and headache. With malaria due to P. vivax and P. malariae the patient frequently suffers relapse because of the ability of these parasites to harbor in liver cells for extended periods of time. In view of the recurrent nature of the disease, chemotherapy is used not only to treat the acute phases, but also on an extended basis as a prophylactic or suppressive therapy. Although there are now available synthetic chemicals for the treatment of malaria, the search has continued for new and/or improved antimalarials and for compounds effective against strains of Plasmodia resistant to currently available agents.